Personal information managed by computers include especially highly confidential information. For example, countries allocate a number to each member to integrally manage information concerning social security and tax payment. The number allocated to each member is called an Individual Number, which is nicknamed as My Number (registered trademark) in Japan. Companies use the Individual Numbers of employees for, for example, tax withholding of income taxes of the employees. Many companies manage the Individual Numbers of the employees using computers.
However, storage of the Individual Numbers in computers increases the risk of external leakage of the Individual Numbers. Individuals are capable of being uniquely identified using the Individual Numbers and the Individual Numbers may be abused for fraud or the like if the Individual Numbers leak out to malicious persons. Accordingly, by law, personal information including the Individual Number is defined as specific personal information, which is obliged to be securely managed. The secure management includes encryption and storage of access logs.
As a technology to encrypt information for management, for example, an encrypted document creating apparatus is proposed, which creates an encrypted document in which only desired portions are encrypted without creating a plaintext document. In addition, a name identification method is also proposed, which enables a name identification process while keeping the personal information confidential. For example, refer to Japanese Laid-open Patent Publication No. 2012-043242 and Japanese Laid-open Patent Publication No. 2013-149056.